jQuery $.ajax(), $.post sending “OPTIONS” as REQUE

Question

Having trouble with what I thought was a relatively simple jQuery plugin...

The plugin should fetch data from a php script via ajax to add options to a <select>. The ajax request is pretty generic:

$.ajax({
  url: o.url,
  type: 'post',
  contentType: "application/x-www-form-urlencoded",
  data: '{"method":"getStates", "program":"EXPLORE"}',
  success: function (data, status) {
    console.log("Success!!");
    console.log(data);
    console.log(status);
  },
  error: function (xhr, desc, err) {
    console.log(xhr);
    console.log("Desc: " + desc + "\nErr:" + err);
  }
});

This seems to work fine in Safari. In Firefox 3.5, the REQUEST_TYPE on the server is always 'OPTIONS', and the $_POST data does not appear. Apache logs the request as type 'OPTIONS':

::1 - - [08/Jul/2009:11:43:27 -0500] "OPTIONS sitecodes.php HTTP/1.1" 200 46

Why would this ajax call work in Safari, but not Firefox, and how do I fix it for Firefox?

Response Headers
Date: Wed, 08 Jul 2009 21:22:17 GMT
Server:Apache/2.0.59 (Unix) PHP/5.2.6 DAV/2
X-Powered-By: PHP/5.2.6
Content-Length  46
Keep-Alive  timeout=15, max=100
Connection  Keep-Alive
Content-Type    text/html

Request Headers
Host    orderform:8888
User-Agent  Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.5; en-US; rv:1.9.1) Gecko/20090624 Firefox/3.5
Accept  text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language en-us,en;q=0.5
Accept-Encoding gzip,deflate
Accept-Charset  ISO-8859-1,utf-8;q=0.7,*;q=0.7
Keep-Alive  300
Connection  keep-alive
Origin  http://ux.inetu.act.org
Access-Control-Request-Method   POST
Access-Control-Request-Headers  x-requested-with

Here is a picture of the Firebug output:

Answer 1

I was looking through source 1.3.2, when using JSONP, the request is made by building a SCRIPT element dynamically, which gets past the browsers Same-domain policy. Naturally, you can't make a POST request using a SCRIPT element, the browser would fetch the result using GET.

As you are requesting a JSONP call, the SCRIPT element is not generated, because it only does this when the Type of AJAX call is set to GET.

http://dev.jquery.com/ticket/4690

Answer 2

I had a similar problem with trying to use the Facebook API.

The only contentType which didn't send the Preflighted request seemed to be just text/plain... not the rest of the parameters mentioned at mozilla here

• Why is this the only browser which does this?
• Why doesn't Facebook know and accept the preflight request?

FYI: The aforementioned Moz doc suggests X-Lori headers should trigger a Preflighted request ... it doesn't.

Answer 3

I have posted a clear example of how to solve this if control the server code of the domain you are POSTing to. This answer is touched on in this thread, but this more clearly explains it IMO.

How do I send a cross-domain POST request via JavaScript?

Answer 4

Try adding the option:

dataType: "json"

Answer 5

I used the following code on Django side to interpret the OPTIONS request and to set the required Access-Control headers. After this my cross domain requests from Firefox started working. As said before, the browser first sends the OPTIONS request and then immediately after that the POST/GET

def send_data(request):
    if request.method == "OPTIONS": 
        response = HttpResponse()
        response['Access-Control-Allow-Origin'] = '*'
        response['Access-Control-Allow-Methods'] = 'POST, GET, OPTIONS'
        response['Access-Control-Max-Age'] = 1000
        # note that '*' is not valid for Access-Control-Allow-Headers
        response['Access-Control-Allow-Headers'] = 'origin, x-csrftoken, content-type, accept'
        return response
    if request.method == "POST":
        # ... 

Edit: it seems to be that at least in some cases you also need to add the same Access-Control headers to the actual response. This can be a little bit confusing, since the request seems to succeed, but Firefox does not pass the contents of the response to the Javascript.

Answer 6

This mozilla developer center article describes various cross-domain request scenarios. The article seems to indicate that a POST request with content type of 'application/x-www-form-urlencoded' should be sent as a 'simple request' (with no 'preflight' OPTIONS request). I found , however, that Firefox sent the OPTIONS request, even though my POST was sent with that content type.

I was able to make this work by creating an options request handler on the server, that set the 'Access-Control-Allow-Origin' response header to '*'. You can be more restrictive by setting it to something specific, like 'http://someurl.com'. Also, I have read that, supposedly, you can specify a comma-separated list of multiple origins, but I couldn't get this to work.

Once Firefox receives the response to the OPTIONS request with an acceptable 'Access-Control-Allow-Origin' value, it sends the POST request.